Radiation Protection in Radiology Large Facilities

Transcription

1 Radiation Protection in Radiology Large Facilities Safety Procedures for the Installation, Use and Control of X-ray Equipment in Large Medical Radiological Facilities Safety Code 35

2 Health Canada is the federal department responsible for helping Canadians maintain and improve their health. We assess the safety of drugs and many consumer products, help improve the safety of food, and provide information to Canadians to help them make healthy decisions. We provide health services to First Nations people and to Inuit communities. We work with the provinces to ensure our health care system serves the needs of Canadians. Published by authority of the Minister of Health Également disponible en français sous le titre : Radioprotection en radiologie Grands établissements Procedures de sécurité pour l installation, l utilisation et le contrôle des appareils à rayons X dans les grands établissements radiologiques médicaux Code de sécurité 35 This publication can be made available on request on diskette, large print, audio-cassette and braille. Her Majesty the Queen in Right of Canada, represented by the Minister of Health Canada, 2008 This publication may be reproduced without permission provided the source is fully acknowledged. HC Pub.: 4000 Cat.: H128-1/08-545E ISBN:

3 Table of Contents Explanatory Notes...3 Acknowledgements...4 Introduction...5 Principal Objectives of the Safety Code...6 Section A: Responsibilities and Protection Responsibility of Personnel Owner Responsible User X-ray Equipment Operator Medical Physicist/Radiation Safety Officer Referring Physician/Practitioner Information Systems Specialist Repair and Maintenance Personnel Procedures for Minimizing Radiation Exposure to Personnel General Requirements and Recommendations Requirements and Recommendations for Operation of Mobile Equipment Requirements and Recommendations for Operation of Radiographic Equipment Requirements and Recommendations for Operation of Radioscopic Equipment Requirements and Recommendations for Performing Angiography Procedures for Minimizing Radiation Exposure to Patients Guidelines for the Prescription of X-ray Examinations Guidelines for Radiological Examinations of Pregnant Women Guidelines for Carrying out X-ray Examinations General Requirements and Recommendations Requirements and Recommendations for Radiographic Procedures Requirements and Recommendations for Radioscopic Procedures Requirements and Recommendations for Angiography Requirements and Recommendations for Computed Tomography Procedures Guidelines for Reduction of Dose to Sensitive Tissues Diagnostic Reference Levels (DRLs) Introduction Application Recommended DRL Values...16 Section B: Facility and Equipment Requirements Facility Requirements General Criteria Design and Plan of X-ray Facility Preparation of Facility Plan Considerations for Room Design and Layout Determination of Parameters Governing Structural Shielding Requirements Shielding Calculations Radiographic Films Radiographic X-Ray Equipment and Dedicated Chest Radiographic Equipment Radioscopic X-Ray Equipment and Angiographic X-Ray Equipment Computed Tomography Equipment Medical X-ray Equipment Requirements Regulatory Requirements for Medical X-ray Equipment Equipment Purchasing Needs Analysis Equipment Specifications Analysis of Vendor Quotation and the Purchase Contract Acceptance Testing Existing Medical X-ray Equipment Retrofitting with Computed Radiography (CR) and Digital Radiography (DR) Systems Equipment Specific Requirements General Requirements Radiographic Equipment Requirements Radioscopic Equipment Requirements Computed Tomography Equipment Requirements Dose and Image Quality Information for Computed Tomography Equipment Image Processing Systems Film-Based Systems X-ray Film Cassette and Screen Darkroom...29 Safety Code 35 1

4 3.1.4 Film Processing Viewbox Digital Imaging Systems Computed Radiography Imaging Plates CR Cassette Electronic Display Picture Archiving and Communications System PACS Implementation Teleradiology Other Equipment Protective Equipment Test Equipment Radiation Protection Surveys General Procedures Survey Report Disposal of X-ray Equipment...37 Section C: Quality Assurance Program Introduction Goals of the Quality Assurance Program Costs-Benefits of the Quality Assurance Program Costs of Quality Assurance Program Benefits of Quality Assurance Program Implementation of Quality Assurance Program Policies and Guidelines Development Establishment of Quality Control Procedures Establishment of Administrative Procedures Acceptance Testing Acceptance Testing Evaluation Quality Control Testing Procedures and Equipment Daily Quality Control Testing Quality Control Tests List Daily Quality Control Tests Daily Quality Control Test Equipment Weekly Quality Control Testing Quality Control Tests List Weekly Quality Control Tests Weekly Quality Control Test Equipment Monthly Quality Control Testing Quality Control Tests List Monthly Quality Control Tests Monthly Quality Control Tests Equipment Quarterly Quality Control Testing Quality Control Tests List Quarterly Quality Control Tests Quarterly Quality Control Tests Equipment Semi-Annual Quality Control Testing Quality Control Tests List Semi-Annual Quality Control Tests Semi-annual Quality Control Tests Equipment Annual Quality Control Testing Quality Control Tests List Annual Quality Control Tests Annual Quality Control Tests Equipment...55 Appendix I: Dose Limits for Occupational Ionizing Radiation Exposures...57 Appendix II: Shielding Information Guides...58 Appendix III: NCRP #49 Methodology for Calculation of Shielding Requirements for Diagnostic X-ray Installations...61 Appendix IV: Shielding Guides for Storage of Radiographic Film...67 Appendix V: Federal/Provincial/Territorial Radiation Safety Agencies...68 Appendix VI: Radiation Emitting Devices Regulations for Diagnostic X-ray Equipment...70 Appendix VII: Facility Radiation Protection Checklist Appendix VIII: Radiation Measurement Units...85 References Safety Code 35

5 Explanatory Notes This document is one of a series of Safety Codes prepared by Health Canada to set out requirements for the safe use of radiation-emitting equipment. This Safety Code has been prepared to provide specific guidance to large medical radiological facilities where diagnostic and interventional radiological procedures are routinely performed using radiographic, radioscopic or computed tomography equipment. Large facilities generally operate more than one type of radiological equipment, or have several suites of the same type of equipment. Most hospitals and computed tomography facilities fall within this category. The requirements and recommendations of this safety code do not apply to radiation therapy facilities and the equipment used in radiotherapy, including radiation therapy simulators, for localization and treatment planning. This Safety Code does not address radiation protection for dental and mammography facilities or small radiological facilities such as chiropractic, podiatry, physical therapy and bone densitometry facilities. For these facilities refer to Health Canada publications Safety Code 30, Radiation Protection in Dentistry, Safety Code 33, Radiation Protection in Mammography, and the Safety Code for Small Medical Radiological Facilities. In a field in which technology is advancing rapidly and where unexpected and unique problems continually occur, this Code cannot cover all possible situations. Blind adherence to rules cannot substitute for the exercise of sound judgement. Recommendations may be modified in unusual circumstances, but only upon the advice of experts in radiation protection. This Code will be reviewed and revised from time to time, and a particular requirement may be reconsidered at any time, if it becomes necessary to cover an unforeseen situation. Interpretation or elaboration on any point can be obtained by contacting the Consumer and Clinical Radiation Protection Bureau, Health Canada, Ottawa, Ontario K1A 1C1. This Safety Code replaces Safety Code 20A and Safety Code 31. The information in this Safety Code is intended for owners of healthcare equipment, physicians, technologists, medical physicists and other personnel concerned with equipment performance, image quality and the radiation safety of the facility. The personnel requirements, safety procedures, equipment and facility guidelines and quality assurance measures detailed in this Safety Code are primarily for the instruction and guidance of persons employed in Federal Public Service departments and agencies, as well as those under the jurisdiction of the Canada Labour Code. Facilities under provincial or territorial jurisdiction may be subject to requirements specified under their statutes. The authorities listed in Appendix V should be contacted for details of the regulatory requirements of individual provinces and territories. The words must and should in this Code have been chosen with purpose. The word must indicates a requirement that is essential to meet the currently accepted standards of protection, while should indicates an advisory recommendation that is highly desirable and is to be implemented where applicable. Safety Code 35 3

6 Acknowledgements This document reflects the work of many individuals. It was prepared and compiled by Mr. Christian Lavoie and Ms. Narine Martel of the Medical X-ray and Mammography Division, Consumer and Clinical Radiation Protection Bureau. Appreciation is expressed to Mr. Yani Picard and other members of the Medical X-ray and Mammography Division for their assistance and advice during the preparation of this code. The contributions of the following organizations, agencies and associations whose comments and suggestions helped in the preparation of this code are gratefully acknowledged: Alberta Cancer Board Alberta College of Medical Diagnostic and Therapeutic Technologists Alberta Employment, Immigration and Industry British Columbia Centre for Disease Control Canadian Association of Radiologists Canadian Nuclear Safety Commission Cancercare Manitoba College of Physicians and Surgeons of Alberta Hôpital D r G.-L Dumont, Moncton, New Brunswick Ontario Association of Medical Radiation Technologists Ontario Safety Association for Community and Healthcare Queen Elizabeth Hospital, Charlottetown, Prince Edward Island Saskatchewan Association of Health Organizations Vancouver General Hospital, British Columbia WorkSafe BC Workers Compensation Board Northwest Territories and Nunavut 4 Safety Code 35

7 Introduction Diagnostic and interventional radiology, are an essential part of present day medical practice. Advances in X-ray imaging technology, together with developments in digital technology have had a significant impact on the practice of radiology. This includes improvements in image quality, reductions in dose and a broader range of available applications resulting in better patient diagnosis and treatment. However, the basic principles of X-ray image formation and the risks associated with X-ray exposures remain unchanged. X-rays have the potential for damaging healthy cells and tissues, and therefore all medical procedures employing X-ray equipment must be carefully managed. In all facilities and for all equipment types, procedures must be in place in order to ensure that exposures to patients, staff and the public are kept as low as reasonably achievable. Diagnostic X-rays account for the major portion of man-made radiation exposure to the general population. Although individual doses associated with conventional radiography are usually small, examinations involving computed tomography and radioscopy can be significantly higher. However, with well-designed, installed and maintained X-ray equipment, and through use of proper procedures by trained operators, unnecessary exposure to patients can be reduced significantly, with no decrease in the value of medical information derived. To the extent that patient exposure is reduced, there is, in general, a decrease in the exposure to the equipment operators and other health care personnel. The need for radiation protection exists because exposure to ionizing radiation can result in deleterious effects that manifest themselves not only in the exposed individuals but in their descendants as well. These effects are called somatic and genetic effects, respectively. Somatic effects are characterized by observable changes occurring in the body organs of the exposed individual. These changes may appear within a time frame of a few hours to many years, depending on the amount and duration of exposure to the individual. Genetic effects are an equal cause for concern at the lower doses used in diagnostic radiology. Although the radiation dose may be small and appear to cause no observable damage, the probability of chromosomal damage in the germ cells, with the consequence of mutations giving rise to genetic defects, can make such doses significant for large populations. Since it is not possible to measure carcinogenic effects at low doses, estimates of the incidences of radiation effects at low doses are based on linear extrapolation from relatively high doses. Due to the uncertainties with respect to radiological risk, a radiation protection risk model assumes that the health risk from radiation exposure is proportional to dose. This is called the linear no-threshold hypothesis. Since the projected effect of a low dose increases the incidence of a deleterious effect only minimally above the naturally occurring level, it is impossible to prove by observation either the validity or falsity of this hypothesis. However, the linear no-threshold hypothesis has been widely adopted in radiological protection and has led to the formulation of the ALARA (As Low As Reasonably Achievable) principle. The ALARA principle is an approach to radiation protection to manage and control exposures to radiation workers and the general public to as low as is reasonable, taking into account social and economic factors. In radiology, there are four main aspects of radiation protection to be considered. First, patients should not be subjected to unnecessary radiographic procedures. This means that the procedures are ordered with justification, including clinical examination, and when the diagnostic information cannot be obtained otherwise. Second, when a procedure is required, it is essential that the patient be protected from excessive radiation exposure during the examination. Third, it is necessary that personnel within the facility be protected from excessive exposure to radiation during the course of their work. Finally, personnel and the general public in the vicinity of such facilities require adequate protection. While regulatory dose limits have been established for radiation workers and the general public, these limits do not apply to doses received by a patient undergoing medical X-ray procedures. For patients, the risk associated with the exposure to radiation must always be weighed against the clinical benefit of an accurate diagnosis or treatment. There must always be a conscious effort to reduce patient doses to the lowest practical level consistent with optimal quality of diagnostic information. Through close cooperation between medical professionals, technologists, medical physicists, and other support staff it is possible to achieve an effective radiation protection program and maintain a high quality medical imaging service. Safety Code 35 5

8 This Safety Code is composed of three sections: Principal Objectives of the Safety Code This Safety Code is concerned with the protection of all individuals who may be exposed to radiation emitted by X-ray equipment used in a large radiological facility. The aim of this Safety Code is to provide radiological facilities with the necessary information to achieve the following principal objectives: 1. to minimize patient exposure to ionizing radiation while ensuring the necessary diagnostic information is obtained and treatment provided; 2. to ensure adequate protection of personnel operating X-ray equipment; 3. to ensure adequate protection of other personnel and the general public in the vicinity of areas where X-ray equipment is used. To assist personnel in achieving these objectives, this Safety Code: Section A: Responsibilities and Protection This section sets out the responsibilities of the owner, responsible user, operators and other staff for the safe installation, operation and control of the equipment, and sets out practices to minimize radiation doses to patients, staff and the public. Section B: Facility and Equipment Requirements This section sets out requirements for the facility design and minimum equipment construction and performance standards. Section C: Quality Assurance Program This section sets out requirements for quality assurance programs including acceptance testing and quality control procedures. A. sets out relative responsibilities of the owner, the X-ray equipment operator, the responsible user, the medical physicist or radiation safety officer, the referring physician, the information systems specialist, and the repair and maintenance personnel; B. presents practices and procedures to minimize doses from X-ray equipment to operators and the public; C. presents practices and procedures for minimizing radiation doses to patients while maintaining adequate image quality; D. presents practices and procedures for ensuring the X-ray equipment is used in a safe manner; E. provides information on facility design and shielding requirements; F. specifies minimum standards of construction and performance for X-ray equipment; G. supplies information required to implement and operate a quality assurance program for the facility; H. provides a list of acceptance tests and quality control tests for various types of X-ray equipment and their accessories; and I. provides a schedule for performing quality control tests. 6 Safety Code 35

9 Section A: Responsibilities and Protection 1.0 Responsibility of Personnel Although staff responsibilities described below are grouped separately, to obtain the optimal level of radiation safety and image quality, it is imperative that full cooperation exists among all concerned parties. 1.1 Owner The owner is ultimately responsible for the radiation safety of the facility. It is the responsibility of the owner to ensure that the equipment and the facilities in which such equipment is installed and used meet all applicable radiation safety standards, and that a radiation safety program is developed, implemented and maintained for the facility. The owner may delegate this responsibility to qualified staff. How this responsibility is delegated will depend upon the number of staff members, the nature of the operation, and on the number of X-ray equipment owned. In any event, the owner must ensure that one or more qualified persons are designated to carry out the roles described below. 1.2 Responsible User The main role of the responsible user is to monitor and manage the radiation safety program of the facility including personnel requirements, equipment performance and safety procedures and to communicate program information with the appropriate staff. There must be at least one person designated as the responsible user. If the responsible user also performs patient examinations, then all of the requirements listed in section A1.3 for the X-ray equipment operator must also be met. The responsible user must: 1. possess qualifications for operating the equipment required by any applicable federal, provincial, or territorial regulations or statutes and be certified according to a recognized standard, such as i) for physicians, the Royal College of Physicians and Surgeons of Canada or by the Collège des médecins du Québec, or ii) for technologists, the Canadian Association of Medical Radiation Technologists or l Ordre des technologues en radiologie du Québec; 2. acquire re-qualification or refresher training according to any applicable federal, provincial, or territorial regulations or statutes and according to a recognized standard, such as i) for physicians, the Royal College of Physicians and Surgeons of Canada or by the Collège des médecins du Québec, or ii) for technologists, the Canadian Association of Medical Radiation Technologists or l Ordre des technologues en radiologie du Québec; 3. ensure that the X-ray equipment, image processing equipment, and auxiliary equipment function correctly and are maintained properly by implementing and maintaining an effective imaging quality assurance program for the facility, including quality control testing, establishing diagnostic reference levels, and record keeping; 4. ensure that the equipment is used correctly, and maintained properly, by competent personnel who are properly trained in the safe operation of the equipment; 5. ensure that inexperienced personnel, including students, operate the equipment only under the direct supervision of a licensed, certified, and experienced X-ray equipment operator until competence in a given clinical procedure is achieved, at which time supervision should be indirectly provided by a supervisor available on-site when needed; 6. establish documented safe operating procedures for the equipment and ensure that operating staff are adequately instructed in them; 7. promulgate documented rules of radiation safety and ensure that staff are made aware of them through training; 8. ensure an investigation is completed of any known or suspected exposures received by personnel that are (a) unusually higher than the usual dose received by that individual, or (b) in excess of 1/20th of the dose limit for radiation workers, specified in Appendix I; 9. ensure that radiation levels in controlled and uncontrolled areas are below the maximum permissible limits such that the annual dose limits to radiation workers and the public, given in Appendix I, will not be exceeded; 10. ensure that an effective communication system is maintained between X-ray equipment operators, referring physicians, medical physicists/radiation Safety Officers and information systems specialists to discuss all matters related to radiation protection of patients and workers; and 11. ensure that the Medical Physicist/Radiation Safety Officer and all operators are provided with a copy of this Safety Code. Safety Code 35 7

10 1.3 X-ray Equipment Operator All X-ray equipment operators have the responsibility of carrying out prescribed radiological procedures in a manner which does not cause any unnecessary exposures to patients, themselves and other workers in the facility. Depending on the type of radiological procedure, the equipment may be operated by a physician, a physician/practitioner or a radiation technologist. All operators must: 1. possess qualifications required by any applicable federal, provincial, or territorial regulations or statutes and be certified according to a recognized standard, such as i) for physicians, the Royal College of Physicians and Surgeons of Canada or by the Collège des médecins du Québec, or ii) for technologists, the Canadian Association of Medical Radiation Technologists or l Ordre des technologues en radiologie du Québec; 2. acquire re-qualification or refresher training according to any applicable federal, provincial, or territorial regulations or statutes and according to a recognized standard, such as i) for physicians, the Royal College of Physicians and Surgeons of Canada or by the Collège des médecins du Québec, or ii) for technologists, the Canadian Association of Medical Radiation Technologists or l Ordre des technologues en radiologie du Québec; 3. have documented training in i) the safe operation of the X-ray equipment and accessories used in the facility, ii) the radiological procedure being performed, iii) patient positioning for accurate localization of regions of interest, iv) all manufacturer-specified quality assurance procedures, if necessary; and v) radiation protection procedures and measures. 4. be familiar with, and have access to, the manufacturer s operator manual for the specific equipment used in the facility; 5. recognize the radiation hazards associated with their work and take measures to minimize them; 6. monitor their radiation exposures with the use of a personal dosimeter, if they are likely to receive a dose in excess of 1/20th of the dose limit to radiation workers specified in Appendix I; 7. have a thorough understanding of safe working methods and appropriate techniques and procedures, including the appropriate use of personal protective equipment; 8. have document clinical training, in accordance to federal, provincial, or territorial statutes and regulations and any relevant professional standards, on new radiological procedures before commencing independent work on patients; 9. strive to eliminate unnecessary radiographic procedures by reducing the number of retakes, and reducing all patient radiation exposures to the lowest practical values; 10. participate fully in the established quality assurance program for the facility, including reporting any change in equipment performance to the responsible user; and 11. understand the recommendations of this Safety Code. 1.4 Medical Physicist/Radiation Safety Officer There must be a Medical Physicist or Radiation Safety Officer to act as an advisor on all radiation protection aspects during the initial stages of construction of the facility, installation of the equipment, and during subsequent operations. Medical physicists are health care professionals with specialized training in the medical applications of physics. A radiation safety officer is the title commonly assigned to a radiation safety specialist who routinely manages a facilities radiation protection program. The medical physicist /radiation safety officer must: 1. possess qualifications required by any applicable federal, provincial, or territorial regulations or statutes and be certified according to a recognized standard, such as i) for medical physicists, the Canadian College of Physicists in Medicine; 2. acquire re-qualification or refresher training according to any applicable federal, provincial, or territorial regulations or statutes and according to a recognized standard, such as i) for medical physicists, the Canadian College of Physicists in Medicine; 3. ensure that the installation complies with all applicable regulatory requirements, by i) assessing the radiation safety of an installation at the time of planning and/or construction of the facility, or when modifications are planned and/or being made to an existing facility, ii) registering the equipment with the appropriate agency when new equipment is purchased, and iii) setting periodic scheduled inspections for the facility. In some jurisdictions, the agency responsible for inspections has the mandate for setting inspection schedules; 8 Safety Code 35

11 4. establish safe working conditions according to the recommendations of this Safety Code and the statutory requirements of federal, provincial, or territorial legislation, where applicable; 5. ensure that established safety procedures are being followed and report any non compliance to the responsible user; 6. review the safety procedures periodically and update them to ensure optimum patient and operator safety; 7. instruct X-ray equipment operators and other personnel participating in X-ray procedures in proper radiation protection practices; 8. carry out routine checks of equipment and facility safety features and radiation surveys; 9. ensure that appropriate radiation survey instruments are available, in good working condition, and properly calibrated; 10. keep records of radiation surveys, including summaries of corrective measures recommended and/or instituted (refer to section B5.1; 11. declare who is to be considered an occupationally exposed person (ie. personnel who may receive a radiation dose in excess of 1/20th of the recommended dose limit for a radiation worker, as specified in Appendix I); 12. organize participation in a personnel radiation monitoring service, such as that provided by the National Dosimetry Services, Health Canada, Ottawa, Ontario K1A 1C1; 13. ensure that all occupationally exposed persons wear personal dosimeters during radiological procedures or when occupational exposures are likely; 14. review, manage and maintain records of occupational exposures received by personnel; 15. investigate each known or suspected case of excessive or abnormal exposure to patients and staff to determine the cause and to take remedial steps to prevent its recurrence; 16. participate in the establishment of diagnostic reference levels; and 17. understand the recommendations of this Safety Code. 1.5 Referring Physician/Practitioner The referring physician/practitioner is the individual authorised to prescribe diagnostic or interventional X-ray procedures. The main responsibility of the referring physician/practitioner is to ensure that the use of X-rays is justified. In some jurisdictions, a registered nurse or nurse practitioner may be authorised by legislation to order X-ray examination. In such cases, the responsibilities of the referring physician/ practitioner listed below would apply to those individuals. It is recommended to contact the appropriate provincial or territorial radiation safety agencies, listed in Appendix V, for information on any applicable provincial or territorial statutes or regulations. The referring physician/practitioner must: 1. possess qualifications required by any relevant federal, provincial, or territorial regulations or statutes and be licensed according to a recognized standard such as i) the Royal College of Physicians and Surgeons of Canada or by the Collège des médecins du Québec; 2. acquire re-qualification or refresher training according to any applicable federal, provincial, or territorial regulations or statutes and according to a recognized standard, such as i) for physicians, the Royal College of Physicians and Surgeons of Canada or by the Collège des médecins du Québec; 3. prescribe an X-ray examination based on professional experience, judgement and common sense; 4. give consideration to alternative, non X-ray utilizing, examinations; and should: 1. be confident that the procedure will improve the patient diagnosis and/or treatment sufficiently in comparison with alternate, non X-ray utilizing, methods of diagnosis and/or treatment; 2. be aware of the risks associated with X-ray procedures. 1.6 Information Systems Specialist Facilities performing digital image processing should have access to an individual who is trained and experienced in maintenance and quality control of information technology software and hardware such as those for PACS and teleradiology equipment. Depending on the facility, the individual may be on-site or available upon request. The required qualification of this individual will depend highly on the type of facility and the type of equipment used in the facility. In all situations, the information systems specialist must ensure confidentiality of patient records. The information systems specialist should: 1. be educated and experienced in information technology; 2. possess equipment-specific training provided by manufacturers, where available; 3. be knowledgeable of networking concepts such as DICOM and HL7; 4. be familiar with the workflow of the facility; 5. understand the policies and procedures in place within the facility; Safety Code 35 9

12 6. understand the importance of and the requirements for an information systems quality assurance program; 7. communicate with staff any changes/upgrades made to the information management equipment hardware or software and the resulting consequences on the operating procedures of the facility. 1.7 Repair and Maintenance Personnel The repair and maintenance personnel are individuals authorised to perform hardware and software repairs and maintenance on X-ray generators, control systems, imaging systems and their operating software. Depending on the facility, these individuals may be on-site or available upon request, but in general, this function is sometime contracted to an outside organization, or to the equipment manufacturer. The required qualification of this individual will depend highly on the type of facility and the type of equipment used in the facility. The repair and maintenance personnel should: 1. have knowledge and training in (i) repair and maintenance of radiological imaging equipment, and (ii) radiation protection principles and procedures; 2. ensure that, after a repair or maintenance procedure, the equipment meets the required regulatory standards or manufacturer specifications; 3. ensure that all repair and maintenance procedures are properly recorded and communicated to the responsible user and other appropriate staff; 4. report any non compliance with the established safety procedures to the responsible user; 5. review the maintenance procedures periodically and update them to ensure optimum patient and operator safety; 6. communicate, if necessary, to staff the need for the appropriate acceptance testing, baseline setting and quality control testing; and 7. follow manufacturers recommendations for the repair and maintenance of equipment. 2.0 Procedures for Minimizing Radiation Exposure to Personnel The required and recommended procedures outlined in this section are primarily directed toward occupational health protection. However, adherence to these will also, in many instances, provide protection to visitors and other individuals in the vicinity of an X-ray facility. The safe work practices and procedures should be regarded as a minimum, to be augmented with additional requirements, when warranted, to cover special circumstances in particular facilities. To achieve optimal safety, responsible users and equipment operators must make every reasonable effort to keep exposures to themselves and to other personnel as far below the limits specified in Appendix I as reasonably achievable. 2.1 General Requirements and Recommendations 1. An X-ray room must not be used for more than one radiological investigation simultaneously. 2. Except for those persons whose presence is essential, all persons must leave the room when the irradiation is carried out. 3. Personnel must, at all times, keep as far away from the X-ray beam as practicable. Direct radiation exposure of personnel by the primary X-ray beam must never be allowed. 4. Deliberate irradiation of an individual for training purposes or equipment evaluation must never occur. 5. All personnel must use available protective devices (refer to section B4.1). 6. All operators of X-ray equipment, together with personnel (i.e., nurses) who routinely participate in radiological procedures, and others, likely to receive a radiation dose in excess of 1/20th of the dose limit to radiation workers specified in Appendix I, must be declared radiation workers and monitor their radiation exposures with the use of a personal dosimeter. 7. Personal dosimeters must be worn and stored according to the recommendations of the dosimetry service provider. When a protective apron is worn, the personal dosimeter must be worn under the apron. If extremities are likely to be exposed to significantly higher doses, additional dosimeters should be worn at those locations on the body. 8. All personal dosimetry records must be maintained for the lifetime of the facility. 10 Safety Code 35

13 9. A female operator should immediately notify her employer upon knowledge that she is pregnant, in order that appropriate steps may be taken to ensure that her work duties during the remainder of the pregnancy are compatible with the recommended dose limits as stated in Appendix I. Depending on the type of facility and on the type of work being performed by the employee, it may not be necessary to remove a pregnant staff member from their duties of operating the X-ray equipment. It is recommended that the decision to remove pregnant workers from their duties include consideration of the radiation exposure risks associated with the employees duties, as determined by a medical physicist or a radiation safety officer. 10. Where there is a need to support weak patients or to support or comfort children, holding devices should be used. If parents, escorts or other personnel are called to assist, they must be provided with protective aprons and gloves, and be positioned so as to avoid the X-ray beam. No person should regularly perform these duties. 11. All entrance doors to an X-ray room should be kept closed while a patient is in the room and must be closed while making an X-ray exposure. 12. X-ray machines which are energized and ready to produce radiation must not be left unattended. 2.2 Requirements and Recommendations for Operation of Mobile Equipment 1. Mobile units should be used only if the condition of the patient is such as to make it inadvisable for the examination to be carried out with a stationary unit in the main X-ray department. 2. During operation, the X-ray beam should be directed away from occupied areas if at all possible, and every effort must be made to ensure that this beam does not irradiate any other persons in the vicinity of the patient. 3. The operator must not stand in the direction of the direct beam and must be least 3 metres from the X-ray tube unless wearing personal protective equipment or standing behind a leaded shield. 4. In a capacitor discharge unit, after an X-ray irradiation has been made, there is a residual charge left in the capacitors. The residual charge can give rise to a dark current and result in X-ray emission even though the irradiation switch is not activated. Therefore, the residual charge must be fully discharged before the unit is left unattended. 2.3 Requirements and Recommendations for Operation of Radiographic Equipment 1. The irradiation should, as a general rule, be controlled from the control panel located in a shielded area. Operators should remain in the shielded area. In the case of special techniques where the operator is required to control the irradiation while at the side of the patient, appropriate protective clothing, in accordance with the requirements of section B4.1, must be worn. 2. The operator must have a clear view of the patient during every X-ray examination and must be able to communicate with the patient and/or attendants without leaving the control booth. 3. Radiographic cassettes must never be held by hand during an irradiation. 2.4 Requirements and Recommendations for Operation of Radioscopic Equipment 1. All persons, with the possible exception of the patient, required to be in the room during radioscopy and spotfilm operation associated with the radioscopic operation must wear protective aprons. Lead shields or curtains mounted on the radioscopic unit are not a sufficient substitute for the wearing of personal protective clothing such as lead aprons. 2. Protective gauntlets should be worn by the radiologist during palpation in every radioscopic examination. During radioscopy, palpation with the hand should be kept to a minimum. 3. All radioscopic examinations should be carried out as rapidly as possible using minimum dose rates and X-ray field size. 4. For each type of radioscopic procedure, an assessment should be made of the physical positions of all personnel to ensure ease of operation of the equipment, visibility of the display, and protection from the radiation field Requirements and Recommendations for Performing Angiography. Angiography is potentially one of the greatest sources of exposure to personnel in radiology, since it requires the presence of a considerable number of personnel close to the patient, radioscopy for extended periods of time and multiple radiographic exposures. For such procedures, all personnel must be aware of the radiation hazards involved and make every effort to adhere to the following requirements and recommendations. Safety Code 35 11

14 1. Full use must be made of the protective devices provided with X-ray equipment such as shielded panels, drapes, bucky slot covers, ceiling-suspended lead acrylic screens, etc. 2. The patient is the largest source of scatter radiation. To avoid this scatter, operate the equipment with the tube under the patient and, if the tube is horizontal, stand on the side of the image receptor. 3. All personnel must wear protective clothing and personnel dosimeters. Protective glasses should also be worn. 4. All personnel who are not required to be immediately adjacent to the patient during the procedure must stand back as far as possible from the patient, while still able to effectively carry out their duties and, if at all possible, should stand behind a protective shield. 5. Special shields in addition to the protective devices provided with the machine should be used. 3.0 Procedures for Minimizing Radiation Exposure to Patients The largest single contributor of man-made radiation exposure to the population is dental and medical radiography. In total, such use of X-rays accounts for more than 90 % of the total man-made radiation dose to the general population. The risk to the individual patient from a single radiographic examination is very low. However, the risk to a population is increased by increasing the frequency of radiographic examinations and by increasing the number of persons undergoing such examinations. For this reason, it is important to reduce the number of radiographs taken, the number of persons examined radiographically, and the doses associated with the examinations. To accomplish this reduction, it is essential that patients must only be subjected to necessary radiological examinations and, when a radiological examination is required, patients must be protected from excessive irradiation during the examination. The required and recommended procedures for the protection of the patient, outlined in this section, are directed toward the physician/practitioner, radiologist, and technologist. They are intended to provide guidelines for elimination of unnecessary radiological examinations and for minimizing doses to patients when radiological examinations are necessary. 3.1 Guidelines for the Prescription of X-ray Examinations Unnecessary radiation exposures of patients can be significantly reduced by ensuring that all examinations are clinically justified. This can be done by adhering, as much as possible, to certain basic recommendations. These recommendations are presented below. 1. The prescription of an X-ray examination of a patient should be based on clinical evaluation of the patient and should be for the purpose of obtaining diagnostic information or patient treatment. 2. X-ray examinations should not be performed if there has been no prior clinical examination of the patient. 3. Radiological screening must not be performed unless, it has been proven that the benefit to the individual examined or the population as a whole is sufficient enough to warrant its use. 4. It should be determined whether there have been any previous X-ray examinations which would make further examination unnecessary, or allow for the ordering of an abbreviated examination. Relevant previous images or reports should be examined along with a clinical evaluation of the patient. 5. When a patient is transferred from one physician or hospital to another any relevant images, or reports should accompany the patient and should be reviewed by the consulting physician. 6. When prescribing a radiological examination, the physician should specify precisely the clinical indications and information required. 7. The number of radiographic views required in an examination must be kept to the minimum practicable, consistent with the clinical objectives of the examination. 8. Before performing X-ray examinations on females of child bearing age (11-55 years), the patient must be asked whether there is any chance that they may be pregnant. Radiological examinations of the pelvic area in women of childbearing age should be undertaken in the ten-day period following the onset of menstruation, since the risk of pregnancy is very small during this period. Care must be taken to protect the foetus from radiation when the X-ray examination is not avoidable. The guidelines in section A3.2 for radiological examinations of pregnant women should be followed. 9. If a radiograph contains the required information, repeat procedures must not be prescribed simply because the radiograph is not of the best diagnostic quality. 10. Specialized studies should be undertaken only by, or in close collaboration with a qualified radiologist. 12 Safety Code 35

15 11. A patient s clinical records should include details of X-ray examinations carried out. More specific guidance for the prescription of imaging examinations is available from the Canadian Association of Radiologists (CAR) in their Diagnostic Imaging Referral Guidelines (CAR 2005). These guidelines provide recommendations on the appropriateness of imaging investigations for the purpose of clinical diagnosis and management of specific clinical/diagnostic problems. The objective of these guidelines is to aid the referring physician/practitioner to select the appropriate imaging investigation and thereby reduce unnecessary imaging by eliminating imaging that is not likely to be of diagnostic assistance to a particular patient and by suggesting alternative procedures that do not use ionizing radiation but offering comparable diagnostic testing accuracy. 3.2 Guidelines for Radiological Examinations of Pregnant Women Radiological examinations of the pelvic area of a woman known to be pregnant simultaneously irradiate the patient s gonads and the whole body of the foetus. Irradiation of the unborn foetus increases the infant s risk of somatic effects and also carries the risk of genetic effects in subsequent offspring. Therefore, every effort should be made to avoid unnecessary irradiation of any woman known to be, or who might be pregnant. Clearly, however, in spite of the possibility of radiation damage, if a radiological examination is required for the diagnosis or management of an urgent medical problem, it must be done, irrespective of whether the patient may or may not be pregnant. The following recommendations apply to X-ray examinations involving pregnant or potentially pregnant women: 1. Only essential investigations should be taken in the case of pregnant or suspected pregnant women. 2. When radiological examinations of the pelvic area or abdomen are required, the exposure must be kept to the absolute minimum necessary and full use must be made of gonadal shielding and other protective shielding if the clinical objectives of the examination will not be compromised. 3. If a radiological examination of the foetus is required, the prone position should be used. This has the effect of shielding the foetus from the softer X-rays and hence reducing the foetal dose. 4. Radiography of the chest, extremities, etc., of a pregnant woman, for valid clinical reasons, should only be carried out using a well-collimated X-ray beam and with proper regard for shielding of the abdominal area. 3.3 Guidelines for Carrying Out X-ray Examinations Next to elimination of unnecessary X-ray examinations, the most significant factor in reducing patient exposure is ensuring that only necessary examinations are performed with good technique. It is possible, for example, to obtain a series of diagnostically-acceptable radiographs and have the patient exposures vary widely because of choice of technique and loading factors used. It is the responsibility of the operator and radiologist to be aware of this and to know how to carry out a prescribed examination with the lowest possible exposure to the patient. The requirements and recommendations that follow are intended to provide guidance to the operator and radiologist in exercising their responsibility toward reduction of patient exposure General Requirements and Recommendations 1. The operator must not perform any examination which has not been prescribed. 2. The exposure of the patient must be kept to the lowest practicable value, consistent with clinical objectives and without loss of essential diagnostic information. To achieve this, techniques appropriate to the equipment available should be used. 3. Particular care, consistent with the recommendations of section A3.2, must be taken when radiological examinations of pregnant or potentially pregnant women are carried out. 4. The X-ray beam must be well-collimated to restrict it as much as is practicable to the area of diagnostic interest. 5. The X-ray beam size must be limited to the size of the image receptor or smaller. 6. For systems with multiple AEC sensors, the AEC sensor(s) covering the area of diagnostic interest should be selected. 7. The X-ray beam should not be directed toward the gonads unless it is absolutely essential, in which case gonads shields must be used whenever the value of the examination is not impaired by such use. Guidelines on the use of gonad shielding are given in section A3.4 of this Code. 8. Shielding must be used where appropriate and practicable to limit the exposure of body tissues. It is particularly important that special effort be made to protect the blood forming organs, gonads and thyroid of children. 9. The focal spot-to-skin distance should be as large as possible, consistent with good radiographic technique. 10. Radiological examinations of infants and children should only be performed using techniques and loading factors which have been modified for size and age. Safety Code 35 13